Fix the condition to allow format.

When a drive is right-clicked, the focus of fileManager is not set to the drive unless it has been left-clicked once before that.

test=manual test on device using a write-protected SD card and USB drive
BUG=636373

Review-Url: https://codereview.chromium.org/2253873002
Cr-Commit-Position: refs/heads/master@{#412731}

ui/file_manager/file_manager/foreground/js/file_manager_commands.js

@@ -504,16 +504,17 @@ CommandHandler.COMMANDS_['format'] = /** @type {Command} */ ({
   canExecute: function(event, fileManager) {
     var directoryModel = fileManager.directoryModel;
     var root = CommandUtil.getCommandEntry(event.target);
-    // |root| is null for unrecognized volumes. Regard such volumes as writable
-    // so that the format command is enabled.
-    var isReadOnly = root && fileManager.isOnReadonlyDirectory();
+    // |root| is null for unrecognized volumes. Enable format command for such
+    // volumes.
+    var isUnrecognizedVolume = (root == null);
     // See the comment in execute() for why doing this.
     if (!root)
       root = directoryModel.getCurrentDirEntry();
     var location = root && fileManager.volumeManager.getLocationInfo(root);
+    var writable = location && !location.isReadOnly;
     var removable = location && location.rootType ===
         VolumeManagerCommon.RootType.REMOVABLE;
-    event.canExecute = removable && !isReadOnly;
+    event.canExecute = removable && (isUnrecognizedVolume || writable);
     event.command.setHidden(!removable);
   }
 });